93 research outputs found
Tradition or Cruelty: Following the History of Small Scale Whaling in Taiji, Japan
No full textabstract: Every season from September to March in Taiji, Japan, around 23,000 dolphins, and other small cetaceans are slaughtered or sold to dolphinariums in the name of a 400-year-old tradition. The word ‘tradition’ is often used to rationalize and justify the terrible acts of animal cruelty, as seen in many countries such as bullfighting in Spain, fox hunting in Britain, Thanksgiving in America, and drive hunting in Japan. However, just because something is deemed as a tradition, does not mean it should not be challenged and judged against the standards of morality. Whale and dolphin hunting has stopped becoming a proud cultural tradition of small-scale subsistence whaling and has become a business run on wholesale slaughter and the exploitation of another species. The disconnect between the past and present has led to an evil distortion of the past.
However, this event cannot simply be explained by blaming solely greed and selfishness for driving this long-lasting tradition. By analyzing poems by Misuzu Kaneko, early hunting methods, memorial services, and graves built in the past and comparing them to the current hunting methods, dolphin shows, and the Taiji Whale Museum, one can determine the variety of factors driving these actions and find the point in time when the intentions of these practices shifted. By having a better understanding of the past and the present, one can follow a once-proud tradition becoming a source to justify unethical and cruel behavior. (abstract
Molecular biology of cell surface layer in gram-negative bacteria. 2. Exosporium structure and substance permeation.
No full textCrystal structure of the membrane fusion protein, MexA, of the multidrug transporter in Pseudomonas aeruginosa
No full textThis research was originally published in Journal of Biological Chemistry. Hiroyuki Akama, Takanori Matsuura, Sachiko Kashiwagi, Hiroshi Yoneyama, Shin-ichiro Narita, Tomitake Tsukihara, Atsushi Nakagawa and Taiji Nakae. Crystal structure of the membrane fusion protein, MexA, of the multidrug transporter in Pseudomonas aeruginosa. Journal of Biological Chemistry. 2004; 279, 25939-25942. © the American Society for Biochemistry and Molecular Biology.The MexAB-OprM efflux pump of Pseudomonas aeruginosa is central to multidrug resistance of this organism, which infects immunocompromised hospital patients. The MexA, MexB, and OprM subunits were assumed to function as the membrane fusion protein, the body of the transporter, and the outer membrane channel protein, respectively. For better understanding of this important xenobiotic transporter, we show the xray crystallographic structure of MexA at a resolution of 2.40 Å. The global MexA structure showed unforeseen new features with a spiral assembly of six and seven protomers that were joined together at one end by a pseudo 2-fold image. The protomer showed a new protein structure with a tandem arrangement consisting of at least three domains and presumably one more. The rod domain had a long hairpin of twisted coiled-coil that extended to one end. The second domain adjacent to the rod α-helical domain was globular and constructed by a cluster of eight short β-sheets. The third domain located distal to the α-helical rod was globular and composed of seven short β-sheets and one short α-helix. The 13-mer was shaped like a woven rattan cylinder with a large internal tubular space and widely opened flared ends. The 6-mer and 7-mer had a funnel-like structure consisting of a tubular rod at one side and a widely opened flared funnel top at the other side. Based on these results, we constructed a model of the MexAB-OprM pump assembly. The three pairs of MexA dimers interacted with the periplasmic α-barrel domain of OprM via the α-helical hairpin, the second domain interacted with both MexB and OprM at their contact site, and the third and disordered domains probably interacted with the distal domain of MexB. In this fashion, the MexA subunit connected MexB and OprM, indicating that MexA is the membrane bridge protein
Crystal structure of the drug discharge outer membrane protein, OprM, of Pseudomonas aeruginosa : Dual modes of membrane anchoring and occluded cavity end
No full textThis research was originally published in Journal of Biological Chemistry. Hiroyuki Akama, Misa Kanemaki, Masato Yoshimura, Tomitake Tsukihara, Tomoe Kashiwagi, Hiroshi Yoneyama, Shin-ichiro Narita, Atsushi Nakagawa and Taiji Nakae. Crystal structure of the drug discharge outer membrane protein, OprM, of Pseudomonas aeruginosa : Dual modes of membrane anchoring and occluded cavity end. Journal of Biological Chemistry. 2004; 279, 52816-52819. © the American Society for Biochemistry and Molecular Biology.The OprM lipoprotein of Pseudomonas aeruginosa is a member of the MexAB-OprM xenobiotic-antibiotic transporter subunits that is assumed to serve as the drug discharge duct across the outer membrane. The channel structure must differ from that of the porintype open pore because the protein facilitates the exit of antibiotics but not the entry. For better understanding of the structure-function linkage of this important pump subunit, we studied the x-ray crystallographic structure of OprM at the 2.56-Å resolution. The overall structure exhibited trimeric assembly of the OprM monomer that consisted mainly of two domains: the membrane- anchoring β-barrel and the cavity-forming ?α-barrel. OprM anchors the outer membrane by two modes of membrane insertions. One is via the covalently attached NH2-terminal fatty acids and the other is the β-barrel structure consensus on the outer membrane-spanning proteins. The β-barrel had a pore opening with a diameter of about 6–8 Å, which is not large enough to accommodate the exit of any antibiotics. The periplasmic α-barrel was about 100 Å long formed mainly by a bundle of α-helices that formed a solvent-filled cavity of about 25,000 Å3. The proximal end of the cavity was tightly sealed, thereby not permitting the entry of any molecule. The result of this structure was that the resting state of OprM had a small outer membrane pore and a tightly closed periplasmic end, which sounds plausible because the protein should not allow free access of antibiotics. However, these observations raised another unsolved problem about the mechanism of opening of the OprM cavity ends. The crystal structure offers possible mechanisms of pore opening and pump assembly
Quantitative measurement of membrane fusions induced by calcium and polyethylene glycol using the porin function
No full textLipopolysaccharide promoted opening of the porin channel
No full textAbstractWe show here that the imipenem (a carbapenem, β-lactam antibiotic)-permeable porin channels (protein D2 or OprD2) of Pseudomonas aeruginosa were closed mostly in the lipopolysaccharide (LPS)-free membrane and were openable by adding LPS to the membrane as assayed by ion conductivity measurements using planar lipid bilayers. Open and closed states of the OprD2 channels exhibited conductivities of about 400 and 30 pS, respectively, in 1 M NaCl. The OprD2 channel in the LPS-containing membrane showed very rapid opening and closing events in a second order and the duration of closure became longer at low membrane potentials
Separation of gate- and channel-forming domains in the pore-forming protein of the outer membrane of Pseudomonas aeruginosa
No full textAbstractThe domains of the pore-forming protein responsible for the gate and channel formations were separated and identified in the outer membrane of Pseudomonas aeruginosa. The proteolytic cleavage of the 46K channel protein, protein D2, yielded two major domains with apparent Mr of 27K and 19K. We identified the 27K polypeptide to be the channel-forming domain by an in vitro permeability assay. The channel size of purified 27K domain was indistinguishable from that of native protein D2. Degradation of the 19K domain into small subfragments increases the channel activity about ten times suggesting that the 19K polypeptide forms the gate or cap
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